/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2007-2008, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotools.caching;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import org.geotools.caching.spatialindex.NodeIdentifier;
/**
* Least-Recently Used Eviction Policy
* <p>
* Removes the oldest items from the cache.
* </p>
*
*
*
*
* @source $URL$
*/
public class LRUEvictionPolicy implements EvictionPolicy {
private Map<NodeIdentifier, Object> queue;
private EvictableTree tree;
public LRUEvictionPolicy(EvictableTree tree) {
this.queue = Collections.synchronizedMap(new LinkedHashMap<NodeIdentifier, Object>(100, .75f, true));
this.tree = tree;
}
public boolean evict() {
synchronized (queue) {
Iterator<NodeIdentifier> it = queue.keySet().iterator();
while (it.hasNext()) {
NodeIdentifier node = it.next();
if (!node.isLocked()) {
try {
node.writeLock();
try {
tree.evict(node);
queue.remove(node);
} finally {
node.writeUnLock();
}
} catch (Exception ex) {
ex.printStackTrace();
return false;
}
return true;
}
}
}
return false;
}
public void access(NodeIdentifier node) {
if (queue.containsKey(node)) {
queue.get(node);
} else if (node.isValid()) {
queue.put(node, null);
}
}
}